Circuit and method for controlling power and performance based on operating environment

ABSTRACT

A power control circuit and corresponding technique for controlling the reduction or augmentation of operating frequency and/or supply voltage utilized by an electronic device. Such control is based on the operating environment of the hardware product employing the electronic device by determining whether the hardware product is interconnected to an external source having at least one enhanced cooling mechanism. As a result, the hardware product is able to operate at full frequency and voltage during certain situations and to operate at a reduced frequency and/or voltage during other situations.

This is a continuation of U.S. Ser. No. 08/850,232 filed May 2, 1997 nowU.S. Pat. No. 5,974,556.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of power management. Moreparticularly, the present invention relates to a circuit and a methodfor configuring an electronic device to operate in one of a plurality ofpower states based on the operating environment of its hardware product.

2. Description of Art Related to the Invention

Over the last few years, there have been many advances in semiconductortechnology. These advances have lead to the development of high-speedelectronic devices operating at higher frequencies and supportingadditional and/or enhanced features. As a result, high-speed electronicdevices normally require more power and dissipate more heat as aby-product than antiquated electronic devices operating at lowerfrequencies.

In order to satisfy customer requirements, battery-powered portablecomputers (e.g., laptop or notebook style computers, hand-heldcomputers, etc.) are implemented with high-speed processors similar tothose implemented in desktop computers. Normally, the heat produced byinternal logic of conventional portable computers is dissipated throughpassive cooling. For portable computers, “passive cooling” involvesspreading the heat uniformly along an interior of its casing.Thereafter, the casing of the portable computer is simply cooled throughconduction, convection and radiation.

In light of the semiconductor technology advances, standard passivecooling techniques are now becoming unable to provide sufficient thermaldissipation for portable computers. When the high-speed processor isoperating at full frequency, the surface temperature of the casing ofthe portable computer tends to rise above a temperature consideredacceptable by the Occupational Safety and Health Association (OSHA)and/or portable computer users. As a result, power usage by conventionalportable computers must be reduced in order to prevent the surfacetemperature of the casing from rising above this temperature.

Commonly, power usage of portable computers is reduced by decreasingprocessor core operating frequency at manufacturing to a static valuewhich will not exceed the portable computer's passive coolingcapability. In general, processor core operating frequency is anexternal clock, or bus frequency, multiplied by a fixed bus ratio whichis set by hardware at processor reset. The processor core operatingfrequency may be decreased by lowering the bus ratio or by lowering thefrequency of the external clock supplied to the processor (hereinafterreferred to as “frequency reduction”). Frequency reduction at a fixedbus ratio may be accomplished by dividing the clock signal before it issupplied to the processor. Alternatively, frequency reduction at a fixedbus ratio may be emulated by periodically halting the clock signal forbrief time intervals so that the average operating frequency is reduced.

Referring to FIG. 1, a graph illustrating power savings realized byconventional frequency reduction of an electronic device (e.g., aprocessor) is shown. It is well-known that a processor is designed tooperate across a frequency range at a specific voltage. This operatingrange 100 is represented as being between points A and B, where (i)point A represents the minimum operating frequency at which theprocessor will operate, and (ii) point B represents the maximumoperating frequency that the processor can support. In theory, to afirst order approximation, power is directly proportional to frequencyas presented herein. Thus, as shown through points C and D, a reductionin the operating frequency of the processor by ten percent (10%) willreduce its total power consumption by ten percent (10%) from P1 to P2.Of course, true system power savings are not exactly proportional tofrequency reduction because most every hardware product, including aportable computer, is implemented with processor frequency-independentcomponents which consume power (e.g., a display).

However, the use of static power saving techniques has generatedperformance gaps between desktop computers and portable computers. Thisperformance gap is a continuing concern to original equipmentmanufacturers (OEMs). One reason is that substantial differences inperformance will adversely effect the demand for portable computers andfor components used therein. To date, it appears that no efforts havebeen made in controlling the reduction or augmentation of the operatingfrequency and/or supply voltage utilized by an electronic device,including a processor, based on the operating environment experienced byits hardware product.

Besides complying with its thermal dissipation constraints, abattery-powered portable computer is configured to reduce its powerusage in order to extend the life of its removable battery packs. Thetypical technique in reducing power usage is not dependent on theoperating environments of the portable computer. Rather, it is usuallydependent on a system dependent, power management system which, througha combination of software and hardware, is able to put unusedsub-systems into sleep or shut-down modes thus saving power.

SUMMARY OF THE INVENTION

The present invention relates to a circuit and method alteringperformance of an electronic device implemented within the hardwareproduct. With respect to the method, at least two operational steps areperformed. First, a determination is made as to whether the hardwareproduct is coupled to an external source having an enhanced coolingmechanism. Thereafter, at least an operating frequency of the electronicdevice is adjusted in response to the determination stated above.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will becomeapparent from the following detailed description of the presentinvention in which:

FIG. 1 is an illustrative diagram of theoretical power savings realizedby a frequency reduction technique when a constant voltage is applied.

FIG. 2A is an illustrative diagram of the theoretical “squared”relationship between voltage and power when a constant frequency isapplied.

FIG. 2B is an illustrative diagram of power savings realized by anelectronic device which is controlled through voltage and frequencyscaling with a variable voltage being the minimum voltage which willsupport that operating frequency.

FIGS. 3A-3F are illustrative diagrams of a hardware product placed intooperating environments which would preferably cause an electronic devicewithin the hardware product to be automatically set into a low powermode, a high power mode and an intermediate power mode, respectively.

FIG. 4 is an illustrative block diagram of a hardware productimplemented with a first embodiment of a power control circuit used toalter the power state of an electronic device through voltage andfrequency scaling.

FIGS. 5A-5C are illustrative flowcharts of the operations performed bythe present invention in order to increase or reduce performance of theelectronic device through voltage and frequency scaling based on theoperating environment of the hardware product of FIG. 4.

FIG. 6 is an illustrative block diagram of a hardware productimplemented with a second embodiment of the power control circuit whichcontrols power state transitions of an electronic device throughfrequency scaling.

FIGS. 7A-7C are illustrative flowcharts of the operations performed bythe present invention in order to increase or reduce performance of anyelectronic device based on the operating environment of its hardwareproduct.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The detailed description describes a power control circuit and methodfor enabling an electronic device to operate in a plurality of powerstates in order to reduce power usage. Selection of the power states isdependent on the operating environment of a hardware product implementedwith the electronic device; namely, whether an external source having anenhanced cooling mechanism is coupled to the hardware product. Althoughcertain details are set forth in order to provide a thoroughunderstanding of the present invention, it is apparent to a person ofordinary skill in the art that the present invention may be practicedthrough many different embodiments, other that those embodimentsillustrated, without deviating from the spirit and scope of the presentinvention. In other instances, well-known circuits, elements and thelike are not set forth in detail in order to avoid unnecessarilyobscuring the present invention.

Herein, a number of terms and symbols are frequently used to describelogic, information or characteristics. An “electronic device” is asingle integrated circuit (IC) component or a multiple IC componentsoperating in tandem. Examples of an electronic device include, but arenot limited or restricted to, a processor, micro-controller, and achipset. “Hardware product” is broadly defined as any commercial ornon-commercial goods having the electronic device. Examples of ahardware product include, but is not limited or restricted to, aportable computer (e.g., a laptop or notebook computer, hand-heldcomputer, etc.), a wireless telephone, camcorder, still-camera, videocassette recorder, set-top cable box, a video game system and the like.A “communication line” is broadly defined as one or moreinformation-carrying mediums (e.g., electrical wire, a bus line, fiberoptics, a wireless communication channel, an infrared “IR” link, a radiofrequency “RF” link, etc.).

In addition, a “bus ratio” (sometimes referred to as “bus-to-corefrequency ratio”) is a code setting the operating frequency of theelectronic device to a selected multiple of a bus frequency. Forexample, if the bus frequency is set to sixty-six megahertz (66 MHz), aparticular code could set the operating frequency of the electronicdevice to be 133 MHz (2×66 MHz). The symbol “#” denotes that a signal isactive-low, although the signal could be modified to be active-high inthe alternative.

Referring to FIG. 2A, an illustrative graph of the theoreticalrelationship between voltage and power at a constant frequency is shown.As noted in Equation 1 below, it is theoretical fact that power has a“squared” law dependence with voltage and a generally proportionalrelationship with operating frequency.

Power=C×V²×F×Act   Equation 1

where

“C”=total capacitance of the electronic device;

“V”=total voltage supplied to the electronic device;

“F”=operating frequency of the electronic device; and

“Act”=percentage of gates of the electronic device changing state for agiven clock cycle.

Thus, according to Equation 1, a ten percent decrease (10%) in voltageat a constant frequency constitutes a nineteen percent (19%) decrease inpower since (0.81)×Power=C×(0.90V)²×F×Act.

Referring now to FIG. 2B, an illustrative graph of the power savingrealized by an electronic device by performing combined voltage andfrequency scaling is shown, when the electronic device is alwaysoperating at the lowest voltage which will support the operatingfrequency. Similar to FIG. 1, the electronic device is operationalwithin a voltage range 200 which is defined between point A (minimumoperating voltage of the electronic device) and point B (maximumoperating voltage). Furthermore, to be consistent with FIG. 1, points Cand D represent voltage range 210 consistent with the operationalfrequency of the electronic device at power states P1 and P2,respectively. Thus, by decreasing the operational frequency and voltageof the electronic device (at point C) by slightly over three percent (topoint D), the power consumed by the electronic device is decreased byapproximately ten percent (10%) since

C×(0.966V)²×(0.966F)×Act≈(0.901)×Power.

Clearly, while the realized power savings is generally equivalent tothat obtained through frequency reduction, the operating frequency ofthe electronic device has diminished only about three percent (3%)rather than ten percent (10%). It is contemplated that voltage andfrequency scaling may occur in voltage range 200; however, onlyfrequency scaling may occur for the electronic device along alow-voltage range 220 up to point A. This is due to the fact thatvoltage scaling in the low-voltage range 220 would cause the electronicdevice to become inoperative.

Referring to FIGS. 3A-3F, illustrative views of different operatingenvironments available to a hardware product (e.g., a portable computer)is shown. For example, as shown in FIG. 3A, a portable computer 300 ispowered from one or more removable battery packs (not shown) for use atany location with or without an alternating current (AC) power supply(e.g., within a vehicle of transport). In this operating environment, itwould be desirable to operate certain electronic devices of portablecomputer 300 at a reduced frequency and/or voltage level (e.g., at a lowpower state) for a number of reasons. One reason is that reduced powerusage would result, extending battery life of portable computer 300.Another reason is that, for this usage, the cooling of the electronicdevices is dependent on the passive cooling implemented in the portablecomputer, possibly augmented with a small, battery operated fan. If itselectronic devices are operating at a high power state, the electronicdevices will exceed their temperature specification which may causeportable computer 300 to fail. Moreover, the surface temperature ofcasing 305 may increase to cause discomfort to the user, adjacentpersons, or to adverse effect material in contact with casing 305.

Referring now to FIG. 3B, portable computer 300 is placed (“docked”) ina docking station 310 and attached to a connector 320 of the dockingstation 310. Connector 320 may be adapted as an interface for portablecomputer 300 to (i) provide thermal reduction through connectivity ofenhanced cooling mechanisms provided by an external source such asdocking station 310, (ii) receive DC power, and (iii) operate as anlogical connection to propagate signals to control various peripheraldevices normally reserved for desktop computers (e.g., an extendedkeyboard, mouse, modem or networking transceiver, compact disk read onlymemory “CD ROM” drive, etc.). It is contemplated, however, that aseparate connector dedicated for enhanced cooling may be employed inlieu of or in combination with connector 320. In this operatingenvironment, it would be desirable to operate an electronic device(s)within portable computer 300 at a high power state, possibly the highestpower state supported by the electronic device(s).

Examples of these enhanced cooling mechanisms may include, but are notlimited or restricted to, the use of heat transfer elements, heatexchangers and/or thermo-electric coolers in combination with one ormore AC-powered fans. Typically, although not shown herein, a firstinterlock mechanism (e.g., a sensor type construction) is employedwithin portable computer 300 in order to generate a signal when portablecomputer 300 is appropriately coupled to docking station 310.

More specifically, as shown in FIG. 3C, one embodiment of an enhancedcooling mechanism may include the implementation of a heat transferelement 322 (e.g., heat pipe) within portable computer 300 to removeheat from at least one electronic device. The heat transfer element 322is thermally coupled to electronic device 324 by directly mountingitself to electronic device 324 or via several heat conductingcomponents (e.g., a heat conducting block affixed using solder, thermalepoxy, or other suitable material).

An end portion 326 of heat transfer element 322 may be exposed through acloseable aperture at a mating end of portable computer 300 when docked.Mechanisms well known in the art may be used to cause a door 328 to openthe closeable aperture, either automatically or manually.

The docking station 310 includes a second heat transfer element 330. Thesecond heat transfer element 330 is secured to the docking station 310by a pair of mounting brackets 332 a and 332 b. Other known mountingmechanisms may be used as is convenient for a particular docking stationconfiguration. For instance, only a single mounting bracket may be used,or more than two mounting brackets may be used. A set of heatdissipation fins 334 as well as second heat transfer element 330 form aheat dissipation mechanism which dissipates heat in docking station 310.

A heat exchange mechanism is formed by joining the heat transferelements 322 and 330 together. One end of the heat transfer element 330conformably engages the end portion 326 of heat transfer element 322when docking station 310 and the portable computer 300 mate. Asillustrated, in one embodiment, the heat exchange mechanism is formed bya female end of the heat transfer element 330 engaging a male connectorend of the heat transfer element 322. Alternately, these mechanisms maybe reversed; however, the smaller male end is more appropriate forportable computer 300.

Another embodiment of an enhanced cooling mechanism may includeimplementation of an air cooling duct system as shown in FIG. 3D. Theheat transfer element 322 is implemented to remove heat from electronicdevice 324. Heat transfer element 322 conveys heat away from electronicdevice 324 to a heat exchange duct 340. A vent 342 allows air to easilyenter or exit a first end of the heat exchange duct 340. Typically, vent342 forms an inlet as cool air is drawn in through heat exchange duct340 and warm air is dispelled at a second end of heat exchange duct 340.Vent 342 may also be covered by a protective screen to reduce the intakeof dust and particles.

The second end of heat exchange duct 340 is positioned at the matingedge of the portable computer 300 aligned with an aperture 344. In oneembodiment, aperture 344 is mechanically opened, and the second end ofthe heat exchange duct 340 exposed, only when portable computer 300 andthe docking station 310 are in a mated (docked) position. In anotherembodiment, the second end of heat exchange duct 340 may be permanentlyexposed to continuously allow connective airflow.

In general, docking station 310 forces air through the portablecomputer's heat exchange duct 340 using one of a variety of forced airmechanisms. The forced air mechanism operatively engages heat exchangeduct 340, meaning that it causes an increased airflow, either drawing orblowing air through that duct 340. The forced air mechanism and the ductneed not be intimately mated, but rather may be positioned in closeproximity to each other, so long as increased airflow through heatexchange duct 340 results. Since docking station 310 and portablecomputer 300 may be mated and unmated, a removably engaged heat exchangemechanism is formed. As discussed above, higher performance may beobtained from portable computer 300 with the additional coolingcapacity.

As further shown in FIG. 3D, the forced air mechanism includes a fan 346and a second heat exchange duct 348. Second heat exchange duct 348 issecured to the housing of docking station 310 by a mounting element 350.The fan 346 is mounted in the housing of docking station 310 to providerelatively unencumbered airflow. Air may flow in either direction;however, it is preferable that fan 346 pull air through ducts 340 and348. Additionally, fan 346 may be mounted in the top, bottom, or eitherside of the docking station as is convenient in a particular dockingstation configuration.

Referring to FIG. 3E, portable computer 300 is directly connected to apower supply brick 360. Power supply brick 360 includes circuitry thatconverts AC power (received from a power cable 370 plugged into anelectrical outlet) into DC power to be provided to portable computer300. Also, power supply brick 360 includes an enhanced cooling mechanismwhich can be used by portable computer 300 to reduce thermal temperatureinside casing 305. In this operating environment, it may be desirable tooperate electronic devices within portable computer 300 at anintermediate power state because (i) DC power is being supplied from anexternal source; and (ii) power supply brick 360 includes an enhancedcooling mechanism (e.g., an AC powered fan). Signaling that power supplybrick 360 is coupled to portable computer 300 is provided through asecond interlock mechanism (not shown). Of course, it is contemplatedthat any number of power states may be supported as shown in FIG. 4.

The cooling effect of power supply brick 360 is illustrated in detail inFIG. 3F in which an alternative position (side) of casing 305, besides arear portion of casing 305, is implemented with a receptacle (port) forpower supply brick 360. In this embodiment, heat transfer element 322conveys heat away from the electronic device 324 to a receptacle 380.Receptacle 380 is formed at an exterior surface of casing 305, althoughthe surface may be recessed and/or receptacle 380 may be protected by acovering or a door when not in use. Receptacle 380 may be either formedas a separate component and affixed to casing 305, or may form a part ofcasing 305 itself.

Receptacle 380 includes a thermal mating connector 382, and a pluralityof electrical connectors 384 a, 384 b, and 384 c. In one embodiment,receptacle 380 is recessed into casing 305 of the portable computer 300and includes male electrical and thermal connectors. In otherembodiments, female connectors, or a combination of male and femaleconnectors, may be used.

A plug 390 includes a plurality of electrical connectors 392 a, 392 b,and 392 c which cooperatively engage the connectors 384 a, 384 b, and384 c, respectively. A thermal mating connector 394 thermally engagesthe thermal mating connector 382 when plug 390 mates with receptacle380. A thermal-electrical cable 396 connected to plug 390 carries a setof electrical conductors 361 and a flexible thermal conductor 362 topower supply brick 360.

Receptacles and plugs are well known mechanisms and any appropriateprior art connector, receptacle, or plug structure may be used. Forexample, the mechanical engaging structures may be changed, as may thenumber, type, or arrangement of the particular electrical connectorsused.

Additionally, any appropriate thermal connectors may be used. In oneembodiment, heat transfer element 322 may include a heat pipe with anopen cylindrical end for thermal mating connector 382. The opencylindrical end is adapted to engage one end of a flexible heat pipeextending from plug 390. The engaging portion flexible heat pipe may bemounted in a similarly shaped copper or other rigid heat conductiveconnector to ensure proper mating with receptacle 380. In other words,an end portion of the heat pipe may be encased in a metal connector.Thus, in one embodiment, the flexible heat pipe or a heat conductiveconnector attached thereto forms thermal mating connector 394, and theflexible heat pipe forms the flexible thermal conductor 362 extendingthrough thermal-electric cable 396 and into power supply brick 360.

Power supply brick 360 is also a heat dissipation brick because itcontains heat dissipation mechanisms in addition to power supplycomponents. In alternate embodiments, these components could be suppliedin separate housings or completely independently of each other. Thecombination, however, advantageously reduces the number of componentsoutside portable computer 300 and allows the use of active (i.e.,requiring electricity) heat dissipation mechanisms. Additionally, inother embodiments, the brick may take different shapes (cylindrical,square, or otherwise), and may perform either no function beyond heatdissipation or one or more additional functions such as power conversionor a data communication function.

As illustrated, power supply brick 360 includes a power supply circuit363. A plug 375 supplies alternating current (AC) from an electricaloutlet to power supply circuit 363 through power cable 370. The powersupply circuit 363 provides power to portable computer 300 via theelectrical conductors 361 and the electrical connectors 392 a, 392 b,and 392 c. Power supply 363 also supplies power to a fan 364 via asecond set of conductors 365.

In the illustrated embodiment, fan 364 cools a heat sink 366 which isattached to a portion 367 of flexible thermal conductor 362 by a topheat dissipation plate 368 a. A bottom heat dissipation plate 368 bfurther removes heat from the flexible thermal conductor 362. In oneembodiment, the heat dissipation plates 368 a and 368 b are copper. Inother embodiments, aluminum or other heat conductive materials may beused. Additionally, one or both of the plates 368 a and 368 b may beeliminated and heat sink 366 may be directly attached to the flexiblethermal conductor 362.

When plug 375 is connected to the electrical outlet and plug 390 ismated with receptacle 380, portable computer 300 can receive additionalpower to improve the performance of certain components such as itsprocessor. The additional heat dissipation mechanism provided by powersupply brick 360 allows such additional power consumption withoutoverheating or damaging components.

Referring now to FIG. 4, an illustrative embodiment of a power controlcircuit employed within a hardware product to control power usage by anelectronic device in light of the existence of enhanced coolingmechanisms is illustrated. In this embodiment, the hardware product andelectronic device are chosen to be illustrated as a portable computerand a processor, respectively. The hardware product is arbitrarily shownas a portable computer. Likewise, the electronic device is shown as aprocessor because of its reputation of being one of the primary powerconsuming electronic devices of a portable computer. However, asalternative embodiments, the power control circuit may be used tocontrol power usage by other types of electronic devices such as acontroller (within a wireless telephone or other hardware product), agraphics controller and chipsets for example.

Portable computer 400 comprises a processor 410 coupled to a firstbridge unit 420 and a power supply circuit 450. While it is well-knownthat first bridge unit 420 operates as a communication gateway betweenprocessor 410 and at least main memory (not shown), it also providesreset capability to processor 410 as shown. More specifically, firstbridge unit 420 is coupled to processor 410 via communication line 411.This enables first bridge unit 420 to transmit an active reset signal(CPURST#) through communication line 411 upon detecting an event such asprocessor 410 accessing a specific input/output (I/O) space. The firstbridge unit 420 is further coupled to a second bridge unit 430 through acommunication line 421 to support information transmissions betweenthese bridge units 420 and 430. In this illustrative example, firstbridge unit 420 is a chipset such as 44OBX™ manufactured by IntelCorporation of Santa Clara, Calif., although it is not limited orrestricted to this type of chipset. The second bridge unit 430 mayinclude a PCI-to-ISA bridge such as a PIIX4™ chipset manufactured byIntel Corporation.

A micro-controller 440 is coupled to second bridge unit 430 to controloperations of a power control circuit 460. The status of the bus ratioand the status of the supply voltage are continuously compared with apredetermined interlock mechanism value by power state transitioncircuit 490. The predetermined value input into a first comparison set(COM) 491 and a second comparison set (COM) 492 depends on whetherportable computer 400 is coupled to a docking station, a power supplybrick, or any other peripheral used to providing enhanced coolingrequirements. If first comparison set 491 (e.g., one or morecomparators) outputs an active signal, it indicates that the status ofthe last bus ratio set differs from a targeted bus ratio associated withthe current operational environment of portable computer 400. Likewise,if the second comparison set 492 outputs an active signal, it indicatesthat the current level of supply voltage differs from an expected supplyvoltage associated with the current operational environment of portablecomputer 400.

Either event would cause the operating system to be notified by aninterrupt such as an Advanced Configuration and Power InterfaceSpecification (ACPI) interrupt. The ACPI interrupt indicates that achange has occurred in the operating environment of portable computer400. The operating system will pass control to micro-controller 440,which is now responsible for transferring control information over asystem management (SM) bus 441 to power control circuit 460 in order toadjust the power state of processor 410.

In this embodiment, power control circuit 460 is implemented withinportable computer 400 and includes a frequency control circuit 470 and avoltage control circuit 480. Frequency control circuit 470 is coupled tomicro-controller 440 through SM bus 441, and is further coupled toprocessor 410, first bridge unit 420 and second bridge unit 430 throughcommunication lines 442-444, respectively. Additionally, voltage controlcircuit 480 is coupled to micro-controller 440 through SM bus 441 andpower supply circuit 450 via communication line 445.

As shown, frequency control circuit 470 is used to load a variable busratio into processor 410 during a reset condition. Frequency controlcircuit 470 includes a first memory element 471. Preferably implementedas non-volatile memory, first memory element 471 is configured tocontain a plurality of bus ratios used to automatically set processor410 to operate at different power states. These bus ratios are set forthas 4-bit values, although any bit width may be used as alternativeembodiments. The first memory element 471 is coupled to a first selectelement 472 (e.g., a multiplexer, combinatorial logic, etc.) via aplurality of input ports 473 ₁-473 _(n) (“n” being a positive wholenumber). Each of the plurality of input ports 473 ₁-473 _(n) is assignedto receive a particular bus ratio. A first register element 474 iscoupled to SM bus 441 and a select port 475 of the first select element471 in order to select which bus ratio is to be output from first selectelement 472 based on control information received from micro-controller440. The status of the last bus ratio set (which is the currentprocessor bus ratio) is stored in register set 493 for comparisonpurposes.

The output of the first select element 472 is transferred to a firstseries of input ports of a second select element 476. A second series ofinput ports is coupled to a corresponding plurality of leads of secondbridge unit 430. For example, when second bridge unit 430 is implementedas a PIIX4™ component, the second series of input ports is coupled tothe following leads via communication line 444; namely, interrupt(INTR), non-maskable interrupt (NMI), ignore numeric error (IGNEE#) andA20 mask (A20M#). The first reset lead (CRESET#) of first bridge unit420 is coupled to a select port 477 of second select element 476 viacommunication line 443. When an active CRESET# signal is placed oncommunication line 443, it causes the bus ratio from first selectelement 472 to be loaded into processor 410 via communication line 442.Otherwise, information normally propagating through communication line444 (e.g., information output from the INTR, NMI, IGNEE# and A20M# leadsof second bridge unit 430) is loaded into processor 410.

Referring still to FIG. 4, used to vary voltage supplied to processor410 by power supply circuit 450, voltage control circuit 480 is coupledto power supply circuit 450 through communication line 445. Thiscommunication line 445 is used to transfer a selected voltage codewhich, in turn, is used to program the amount of supply voltage providedto processor 410 via communication line 446. The programming of powersupply circuit 450 may be performed through a number of schemes. Forexample, as shown, a plurality of voltage codes may be contained in asecond memory element 481. Of these voltage codes, a first voltage codesignals power supply circuit 450 to provide a base (or minimum) voltageto processor 410. The remaining voltage codes would represent uniquevoltages which are greater than the base voltage. As an alternativeembodiment, the voltage codes may be configured so that each voltagecode represents equivalent voltage increments throughout a voltage rangesupported by processor 410 beginning at a minimum voltage (Vmin) set bypower supply circuit 450 (e.g., a first voltage code signals powersupply circuit 450 to provide a supply voltage equal to (Vmin+0.05)volts, a m^(th) voltage code signals to provide a supply voltage of((Vmin+(m×0.05)) volts.

Voltage control circuit 480 includes the second memory element 481, athird select element 482 and a second register element 483. The secondmemory element 481, preferably implemented as non-volatile memory,contains programmable voltage codes which may be programmed duringmanufacture. The second memory element 482 may be a separate component,or alternatively, may be configured as a particular storage location ofmemory contained in first memory element 471. The voltage codes aretransferred into input ports of third select element 482. Under controlof the micro-controller 440, second register element 483 controlsselection of which voltage code is output to power supply circuit 450.

Referring now to FIGS. 5A-5C, the operations of the power controlcircuit of FIG. 4 in scaling the voltage and frequency of the processorin order to adjust power usage of the portable computer is shown. First,a determination is made whether the operating environment of theportable computer matches the current voltage and frequency setting orhas changed, requiring at least the processor to undergo a power statetransition (Step 500). This may be accomplished through internal logic(e.g., interlock mechanisms) signaling that a certain event has occurredwhich requires a change in power state (e.g., dock a portable computerin a docking station, connect to an operational power supply brick,etc.).

If no alteration of the power state is necessary, the power controlcircuit maintains the portable computer in its current power state.However, if the operating environment has changed, a determination ismade if the operating environment has transitioned to a higher powerstate than its current power state (Step 510). For example, a transitionfrom a low power state to an intermediate or high power state; atransition from an intermediate power state to a high power state; ortransition from one intermediate power state to a higher intermediatepower state.

In the case where the transition is to a higher power state than before,an interrupt is made requesting control of power management to be passedto the micro-controller, which is now responsible for controllingoperating characteristics, in this case an increase of supply voltageand operating frequency (Steps 520 and 525). First, the micro-controllersignals the voltage control circuit to program the power supply circuitto increase the supply voltage to an appropriate level prescribed forthe higher power state (Step 530). This increase in the supply voltageis applied immediately. Next, the micro-controller signals the frequencycontrol circuit to increase the operating frequency of the processor toan operating frequency prescribed for the higher power state by loadinga particular bus ratio (Step 535). However, this increase is not applieduntil after the processor is reset.

Before resetting the processor, processor state information is storedfor retrieval at a later time (Step 540). Then, the processor is resetby activating CPURST#. Concurrent to the activation of CPURST#, CRESET#is a signal which is activated and stays active for a sufficient timeafter CPURST# is removed to cause the particular bus ratio to be loadedinto the processor (Step 545). Thereafter, the processor stateinformation is restored and the processor resumes operations at thehigher supply voltage and operating frequency (Step 550).

In the case where the transition is to a lower power state, an interruptis made requesting control of the power management to be passed to themicro-controller (Steps 555 and 560). The micro-controller signals thefrequency control circuit to decrease the operating frequency of theprocessor to a prescribed operating frequency (Step 565). This isaccomplished by initially storing processor state information, andthereafter, resetting the processor and loading a reduced bus ratiothrough activation of CPURST# and CRESET# signals, respectively (Steps570 and 575). As a result, the bus ratio corresponding to the decreasedoperating frequency is loaded into the processor.

Next, the micro-controller signals the voltage control circuit toprogram the power supply circuit to decrease the supply voltage to anappropriate level prescribed for the lower power state (Step 580). Thisdecrease in the supply voltage is applied immediately by the powersupply circuit. Thereafter, the processor state information is restoredand the processor resumes operations at the lower supply voltage andoperating frequency (Step 585).

Referring to FIG. 6, another illustrative embodiment of the powercontrol circuit employed within a hardware product is shown. Thehardware product (e.g., portable computer 400) comprises processor 410,first bridge unit 420, second bridge unit 430, micro-controller 440,power supply circuit 450, and a power control circuit 600. In thisembodiment, the power control circuit 600 is used to load an updated busratio into processor 410 during a reset condition. Thus, even thoughthis technique does not provide optimal power savings with minimalchange in operating frequency, the operating frequency of processor 410may be altered to lower the power state of processor 410 and power usageby portable computer 400.

In this embodiment, power control circuit 600 includes a memory element610. Preferably implemented as non-volatile memory, memory element 610is configured to contain a plurality of bus ratios used to place theportable computer 400 is different power state. These bus ratios areinput into a first select element 620. Controlled by micro-controller440, a register element 630 is coupled to a select port of first selectelement 620 in order to select which bus ratio is to be outputtherefrom. Likewise, a register set 645 is used to temporarily store thestatus of the last bus ratio set. This status is used by a comparatorset 651 of power state transition circuit 650 to determine whether ornot a change in power state should occur based on detection of thepresence of an external source with an enhanced cooling mechanism.

The selected bus ratio is loaded into a first series of input ports of asecond select element 640. This bus ratio is loaded into processor 410upon the first bridge unit 420 transmitting an active CRESET# signal tosecond select element 640. This is performed when processor 410 is resetto receive the updated bus ratio. Otherwise, information normallypropagating through INTR, NMI, IGNEE# and A20M# leads of second bridgeunit 430 are loaded into processor 410.

Referring now to FIGS. 7A-7C, the operations of the circuit implementedin altering at least the operating frequency of an electronic device,and possibly the supply voltage as denoted by dashed line boxes. Theoperating frequency (and perhaps voltage) is altered based on anoperating environment of the hardware agent employing the electronicdevice. This is performed in order to adjust power usage of the hardwareproduct as necessary. By adjusting power usage due to the hardwareproduct's operating environment, sub-system temperature of the hardwareproduct can be controlled as well as other characteristics (e.g.,battery life).

First, a determination is made whether the operating environment of thehardware product has changed, requiring the electronic device to undergoa power state transition (Step 700). This may be accomplished through anumber of well-known mechanisms. For example, during power-up of thehardware product, it may be configured to initially perform at a certainpower state (e.g., a high power state) and then, to signal circuitry orsoftware controlling power management to transition to a predeterminedpower state based on the current operating environment of the hardwareproduct. Further power state transitions may be monitored throughmechanical interlock comparison with power state.

If no power state transition is necessary, the circuit maintains thehardware product in its current power state. However, if a power statetransition is necessary, a determination is made if the operatingenvironment has transitioned to a higher power state than its currentpower state (Step 710). In the case where the transition is to a higherpower state, control of power management may be passed to an agent(e.g., circuitry and/or software) which is now responsible forcontrolling an increase of possibly supply voltage and operatingfrequency. As an optional step, this agent causes a power supply circuitfor the hardware product to increase the supply voltage to anappropriate level prescribed for the higher power state (Step 720). As arequisite step, the agent causes an increase of the operating frequencyof the electronic device to a prescribed operating frequency associatedwith the detected operating environment (Step 725). This may beaccomplished by loading a code into the electronic device. The code maybe interpreted by the electronic device as a command to operate as acertain operating frequency or to increase or decrease the operatingfrequency by a certain amount.

Thereafter, the electronic device resumes operations at the highersupply voltage and a higher operating frequency (Step 730).

In the case where the transition is to a lower power state, control ofpower management may be passed to an agent (e.g., circuitry and/orsoftware) which is now responsible for controlling a decrease ofpossibly supply voltage and operating frequency. As a requisite step,the agent causes a decrease in operating frequency of the electronicdevice to a prescribed operating frequency associated with the detectedoperating environment (Step 740). This may be accomplished in a manneras described above. As an optional step, this agent causes a powersupply circuit for the hardware product to decrease the supply voltageto an appropriate level prescribed for the lower power state (Step 745).Thereafter, the electronic device resumes operations at the loweroperating frequency and possibly lower supply voltage in order to reducepower usage of the hardware product (Step 750).

The present invention described herein may be designed in many differentembodiments evident to one skilled in the art than those describedwithout departing from the spirit and scope of the present invention.The invention should, therefore, be measured in terms of the claimswhich follow.

What is claimed is:
 1. A method comprising: determining whether ahardware product is coupled to a power supply brick by a flexiblethermal-electrical cable, the power supply brick including circuitrythat converts alternating current (AC) power into direct current (DC)power and an enhanced cooling mechanism; and adjusting at least anoperating frequency of an electronic device implemented within thehardware product from a first operating frequency to a second operatingfrequency in response to determining that the hardware product Iscoupled to the power supply brick having the enhanced cooling mechanism,the second operating frequency corresponding to a power state from oneof at least three power states for the electronic device.
 2. The methodof claim 1, wherein the act of adjusting includes increasing theoperating frequency to the second operating frequency, being higher thanthe first operating frequency, in response to determining that thehardware product is coupled to the power supply brick having theenhanced cooling mechanism.
 3. The method of claim 2, wherein the act ofadjusting further includes adjusting a supply voltage of the electronicdevice from a first voltage level to a second voltage level prior toincreasing the operating frequency to the second operating frequency. 4.The method of claim 3, wherein the first voltage level is equivalent tothe second voltage level, provided the first voltage level and thesecond voltage level are capable of operating in connection with thesecond operating frequency.
 5. The method of claim 1, wherein theoperating frequency is decreased through throttling a clocking signal,normally used to produce the first operating frequency, to produce thesecond operating frequency.
 6. The method of claim 1, wherein the act ofadjusting includes decreasing the operating frequency to the secondoperating frequency, being less than the first operating frequency, inresponse to determining that the hardware product is decoupled from theenhanced cooling mechanism.
 7. The method of claim 6, wherein the act ofadjusting further includes adjusting a supply voltage of the electronicdevice from a first voltage level to a second voltage level afterdecreasing the operating frequency to the second operating frequency. 8.The method of claim 7, wherein the second voltage level is less than thefirst voltage level in order to optimize power reduction.
 9. The methodof claim 1, wherein the hardware product is a portable computer.
 10. Themethod of claim 9, wherein the enhanced cooling mechanism includes aheat transfer element to engage with a heat transfer element located inthe hardware product.
 11. The method of claim 1, wherein the hardwareproduct is a camcorder.
 12. The method of claim 1, wherein the enhancedcooling mechanism is an air cooling duct system including a fan and afirst heat exchange duct to be connected to a second heat exchange ductof the hardware product.
 13. The method of claim 12, wherein the heatexchange duct of the hardware product is coupled to a heat transferelement that conveys heat from the electronic device to air in thesecond heat exchange duct.
 14. The method of claim 12, wherein the fanof the air cooling duct system causes increased airflow through thefirst and second heat exchange ducts.
 15. The method of claim 1, whereinthe enhanced cooling mechanism is a heat sink, a fan situated proximateto the heat sink to cool the heat sink, and a flexible heat pipe havinga first end coupled to the heat sink and a second end for coupling to aheat pipe in the hardware product that conveys heat away from theelectronic device.
 16. The method of claim 1, wherein determiningwhether a hardware product is coupled to an enhanced cooling mechanismby comparing a predetermined interlock mechanism value with a status ofbus ratio and status of supply voltage in the hardware product.
 17. Amethod comprising: determining whether a hardware product is coupled toa power supply brick by a flexible thermal-electrical cable, the powersupply brick including circuitry that converts alternating current (AC)power into direct current (DC) power and an enhanced cooling mechanism;and adjusting a power state of an electronic device implemented withinthe hardware product from a first power state to a second power state inresponse to determining that the hardware product is coupled to thepower supply brick having the enhanced cooling mechanism, the secondpower state being one of at least three power states for the electronicdevice.
 18. The method of claim 17, wherein the adjusting to the secondpower state includes applying a voltage to the electronic device at avoltage -level greater than a voltage level associated with the firstpower state.
 19. The method of claim 17, wherein the adjusting to thesecond power state further includes increasing a clocking signal from afirst operating frequency at the first power state to a second operatingfrequency at the second power state being greater than the firstoperating frequency of the first power state.
 20. The method of claim 7,wherein the determining includes checking whether the hardware productis currently powered by one or more batteries.
 21. The method of claim17, wherein the adjusting to the second power state includes applying avoltage to the electronic device at a voltage level less than or equalto a voltage level associated with the first power state.
 22. The methodof claim 17, wherein the enhanced cooling mechanism is a heat sink, afan situated proximate to the heat sink to cool the heat sink, and aflexible heat pipe having a first end coupled to the heat sink and asecond end for coupling to a heat pipe in the hardware product thatconveys heat away from the electronic device.
 23. The method of claim17, wherein determining whether a hardware product is coupled to anenhanced cooling mechanism by comparing a predetermined interlockmechanism value with a status of bus ratio and status of supply voltagein the hardware product.
 24. A circuit adapted to alter performance ofan electronic device implemented within a hardware product, the circuitcomprising: a control circuit to adjust a power state; and a power statetransition circuit coupled to the control circuit, the power statetransition circuit to detect a change in an operating environment of thehardware product in response to the hardware product being coupled to apower brick by a flexible thermal-electrical cable, the power brickincluding circuitry that converts alternating current (AC) power intodirect current (DC) power and an enhanced cooling mechanism.
 25. Thecircuit of claim 24, wherein the hardware product is a portablecomputer.
 26. The circuit of claim 25, wherein the enhanced coolingmechanism includes a heat transfer element to engage with a heattransfer element located in the hardware product.
 27. The circuit ofclaim 24, wherein the hardware product is a camcorder.
 28. The circuitof claim 24, wherein the enhanced cooling mechanism is an air coolingduct system including a fan and a first heat exchange duct to beconnected to a second heat exchange duct of the hardware product. 29.The circuit of claim 28, wherein the heat exchange duct of the hardwareproduct is coupled to a heat transfer element that conveys heat from theelectronic device to air in the second heat exchange duct.
 30. Thecircuit of claim 28, wherein the fan of the air cooling duct systemcauses increased airflow through the first and second heat exchangeducts.
 31. The circuit of claim 28, wherein the enhanced coolingmechanism is a heat sink, a fan situated proximate to the heat sink tocool the heat sink, and a flexible heat pipe having a first end coupledto the heat sink and a second end for coupling to a heat pipe in thehardware product that conveys heat away from the electronic device. 32.The method of claim 24, wherein detecting a change in an operatingenvironment of the hardware product by comparing a predeterminedinterlock mechanism value with a status of bus ratio and status ofsupply voltage in the hardware product.
 33. A computer comprising: aprocessor implemented in a hardware product; and a control circuitcoupled to the processor, the control circuit to adjust a power state ofthe processor in response to detecting that the hardware product iscoupled to a removable enhanced cooling a mechanism by a flexiblethermal-electrical cable, the control circuit comparing a predeterminedinterlock mechanism value with a status of bus ratio and status ofsupply voltage in the hardware product to adjust the power state to oneof at least three power states for the processor.
 34. The computer ofclaim 33, wherein the detecting includes the processor being suppliedwith a voltage by a power supply brick..
 35. A hardware productcomprising: an electronic device configured to operate in one of atleast two power states; a receptacle on an exterior surface of a casingthat encloses the electronic device, the receptacle including aplurality of electrical connectors and a thermal connector; a powersupply brick including circuitry that converts alternating current (AC)power into direct current (DC) power and an enhanced cooling mechanism;a thermal-electrical cable that flexibly couples the power supply brickand the receptacle, the thermal-electrical cable including a pluralityof electrical conductors and a flexible thermal conductor; and, a powerstate transition circuit coupled to the electronic device to select oneof the at least two power states responsive to coupling of the powersupply brick to the receptacle.
 36. The hardware product of claim 35,wherein the power state transition circuit detects a change in anoperating environment of the hardware product by comparing apredetermined interlock mechanism value with a status of bus ratio andstatus of supply voltage in the hardware product.
 37. The hardwareproduct of claim 35, wherein the power state transition circuit detectsthe electronic device being powered by one or more batteries.
 38. Thehardware product of claim 35, wherein the power state transition circuitdetects the electronic device being supplied with a voltage by the powersupply brick.
 39. The hardware product of claim 35, wherein the enhancedcooling mechanism further comprises a fan.
 40. The hardware product ofclaim 39, wherein the flexible thermal conductor is a heat pipe.
 41. Thehardware product of claim 35, wherein the enhanced cooling mechanismfurther comprises an active heat dissipation mechanism.